Black Sabbath bassist Geezer Butler says the band’s 1970 hit “Paranoid” almost didn’t get recorded out of fear that it sounded too much like Led Zeppelin’s “Communication Breakdown.”

Speaking with Classic Rock, Butler says he and singer Ozzy Osbourne were so concerned that the song would be seen as a Zeppelin rip-off that they refused to play the cut. It was left to guitarist Tony Iommi, who had written the song’s driving guitar riff, to convince them otherwise.

As most fans know, “Paranoid” was written and recorded as a filler track for the group’s second album. In Guitar World’s March 2004 issue, Butler revealed, “We recorded the whole [album] in about two or three days, live in the studio. The song ‘Paranoid’ was written as an afterthought. We basically needed a three-minute filler for the album, and Tony came up with the riff. I quickly did the lyrics, and Ozzy was reading them as he was singing.”

Butler tells Classic Rock that at the time the band was heavily into Led Zeppelin, who had released their self-titled debut containing “Communication Breakdown” in January 1969.

“We always loved Zeppelin in them days, sitting round on the floor smoking dope and listening to that first album,” Butler says. “So when Tony came up with the riff to ‘Paranoid’ me and Ozzy spotted it immediately and went: ‘Naw, we can’t do that!’

“In fact we ended up having quite a big argument about it. Guess who was wrong? The fact that it became such a big hit for us—and is now probably our best known song—says it all, really.”

“Paranoid” had such obvious hit potential that the band decided to name their album after it. The album was originally going to be called War Pigs, after the song’s lead track.

“The irony is,” Butler tells Classic Rock, “Zeppelin also ‘borrowed’ quite a few riffs for some of their best-known songs too. But that’s the thing about rock ‘n’ roll, everyone does that, especially when they’re young and just starting out. It’s putting your own stamp on it that counts. And Sabbath certainly did that.”

According to former Sabbath drummer Bill Ward, the recording of “Paranoid” was a quick affair. “It was about 1:30 in the afternoon and Tony had the riffs,” he says. “By 2:00 we had ‘Paranoid’ exactly as you hear it on the record.”

Check out the original promotional video for the song below, followed by a live Led Zeppelin performance of "Communication Breakdown" from 1969.